The present invention relates generally to sensor arrays and more particularly to normalizing and calibrating a sensor array.
An array of sensors can be used to detect and/or measure the dimension of defects in metal components and parts. In this regard, each sensor in the array is capable of producing an electrical signal indicative of a defect in a metal component or part. Multiple sensors can be used together as an array to scan an area of the component or part that is larger than if a single sensor was used. However, in order to accurately detect and/or measure the defect, it is important that all of the sensors in the array react in the same way (i.e., produce the same electrical signal) to the same defect. For this to occur, the sensors in the array should all have the same dynamic range and respond identically in signal amplitude to the same defect.
To obtain uniform reaction from sensors, the sensors are normalized and calibrated. For example, flexible eddy current array sensors used to inspect aircraft engine components have been previously normalized and calibrated using two separate specimens, one to normalize the signal from all sensor elements and the other to calibrate the element signal level. For normalization, all elements are scanned across a linear feature. A correction factor and offset is calculated for each element from its signal level and saved for use during later testing of a part. For calibration, one of the sensor elements is used to scan a single notch on a test specimen in two dimensions. This process can be time consuming because a significant amount of time is required to properly align the sensor array to each test specimen. In this regard, the sensor needs to be aligned with the test specimen at minimum two times. Furthermore, the two-dimensional scan is done at a high spatial resolution. Moreover, the result's accuracy is limited because the data are obtained using a test specimen that may not match the geometric shape of the part to be inspected so the part test conditions may not match the calibration conditions. Thus, the data may not sufficiently represent the scanning conditions of a sensor array used to scan components or parts having complex surfaces.